Ve Ching in a Small Box

Why is it that cats like lying in small spaces? Here, Ve Ching has squeezed himself into a box that my PDA came in. Note how one side of the box is pushed outwards by his back and bits of him are sticking out of it. The first cat bed that we bought was hardly used until Loy Loy came along. I think the kitties didn't like it cause it didn't fit snugly around them. So when Loy Loy came to live with us, although she was a very small dog, smaller than a couple of the cats, she made the cat bed her own. I guess dogs don't like it snug unlike cats.